In recent years, as a part of the development of new and renewable energy to reduce carbon emissions according to environmental regulations, solar cells, which are capable of converting solar energy into electrical energy so that there are few restrictions on the installation site and electric power can be easily generated, have been attracting attention.
Such a solar cell is manufactured using a monocrystalline or polycrystalline silicon wafer, but monocrystalline silicon is generally used most widely in the field of large-scale power generation systems due to having higher photoelectric conversion efficiency. However, such monocrystalline silicon is uneconomical because of its complicated manufacturing process and high price.
Accordingly, despite relatively low efficiency, a method of manufacturing a solar cell using polycrystalline silicon using a low-grade silicon wafer has been developed and is currently being used in power generation systems for residential use and the like. However, this process is also complicated, and there is a limit to lowering the manufacturing cost of the solar cell due to the increase in the price of raw materials attributable to the price of silicon.
Accordingly, as a thin film solar cell for overcoming this problem, a method of using amorphous silicon having a multi junction structure and a method of using a compound semiconductor such as a chalcogenide-based compound have been developed recently.
Among them, a solar cell manufactured using Cu(In1-xGax)Se2 (hereinafter, referred to as CIGS) which is a chalcogenide-based compound as a CIGS light absorbing layer has been evaluated as a highly efficient and low cost candidate.